Differential thrust vectoring system

ABSTRACT

A differential thrust vectoring system includes a first thruster, a second thruster, a main actuator, and a trim actuator. The system is configured such that actuation of the main actuator causes rotation of the thrusters together about an axis, whereas actuation of the trim actuator causes relative rotation of the first and second thrusters about the axis.

BACKGROUND

Similar to tiltrotor aircraft, compound helicopters aspire to combinethe vertical takeoff and landing, as well as hovering, capabilities of atraditional helicopter with the range and speed of an airplane. In orderto accomplish this goal, compound helicopters generally include atraditional helicopter rotor to provide lift and directional thrustduring low-speed horizontal movement and forward-facing thrusters andfixed wings to provide forward thrust and vertical lift in high speedforward-flight. Various types of forward-facing thrusters have beenincluded on compound helicopters, including jet engines and propellers.Various means have also been implemented to counter the torque effect ofthe main rotor, such as including a traditional tail rotor, havingdifferent blade pitch on the opposing forward-facing propellers, or byusing coaxial contra-rotating rotors.

Placing a fan inside a duct can result in a system that produces morethrust for the same power. This increase in thrust is produced becausethe shape of the duct allows the duct to carry a thrust force. In orderto maximize efficiency, ducts typically place the fan in a generallycylindrical section of the duct and include a generally quarter toroidalinlet upstream of the fan and a generally frusto-conical diffusersection downstream of the fan. This arrangement accelerates the airacross the inlet and decelerates the air at the diffuser, therebycreating a pressure differential on the duct across the fan disk,resulting in additional thrust. However, the duct must have a sufficientlength to fully decelerate the airflow in order to maximize theadditional thrust. As such, fitting ducts around the forward-facingpropellers of a compound helicopter would create large surfaces thatwould suffer ill effects from the downwash of the main rotor whilehovering.

BRlEF DESCRlPTION OF THE DRAWINGS

FIG. 1 is an oblique view of an aircraft in a forward-flight mode withthrusters having aligned thrust vectors, according to this disclosure.

FIG. 2 is an oblique view of the aircraft of FIG. 1 in a hover mode withthe thrusters having skewed thrust vectors.

FIG. 3 is an oblique view of a thruster of the aircraft of FIG. 1

FIG. 4A is an oblique view of a first portion of a differential thrustvectoring system, according to this disclosure.

FIG. 4B is a top view of the differential thrust vectoring system ofFIG. 4A.

FIG. 4C is an oblique view of a second portion of the differentialthrust vectoring system of FIG. 4A.

FIG. 5A is an oblique view of another differential thrust vectoringsystem, according to this disclosure.

FIG. 5B is a top view of the differential thrust vectoring system ofFIG. 5A.

FIG. 6A is an oblique view of a first portion of another differentialthrust vectoring system, according to this disclosure.

FIG. 6B is a top view of the differential thrust vectoring system ofFIG. 6A.

FIG. 6C is an oblique view of a second portion of the differentialthrust vectoring system of FIG. 6A.

DETAILED DESCRIPTION

While the making and using of various embodiments of this disclosure arediscussed in detail below, it should be appreciated that this disclosureprovides many applicable inventive concepts, which can be embodied in awide variety of specific contexts. The specific embodiments discussedherein are merely illustrative and do not limit the scope of thisdisclosure. In the interest of clarity, not all features of an actualimplementation may be described in this disclosure. It will of course beappreciated that in the development of any such actual embodiment,numerous implementation-specific decisions must be made to achieve thedeveloper's specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother.

In this disclosure, reference may be made to the spatial relationshipsbetween various components and to the spatial orientation of variousaspects of components as the devices are depicted in the attacheddrawings. However, as will be recognized by those skilled in the artafter a complete reading of this disclosure, the devices, members,apparatuses, etc. described herein may be positioned in any desiredorientation. Thus, the use of terms such as “above,” “below,” “upper,”“lower,” or other like terms to describe a spatial relationship betweenvarious components or to describe the spatial orientation of aspects ofsuch components should be understood to describe a relative relationshipbetween the components or a spatial orientation of aspects of suchcomponents, respectively, as the device described herein may be orientedin any desired direction. In addition, the use of the term “coupled”throughout this disclosure may mean directly or indirectly connected,moreover, “coupled” may also mean permanently or removably connected,unless otherwise stated.

This disclosure divulges differential thrust vectoring systems and anaircraft for use thereon. Each differential thrust vectoring systemdisclosed herein is configured to enable rotation of a pair of thrustersof an aircraft relative to the fuselage by varying amounts. Thedifferential thrust vectoring systems include a first thruster rotationassembly with a first spindle coupled for common rotation with a firstthruster and a second thruster rotation assembly with a second spindlecoupled for common rotation with a second thruster. The differentialthrust vectoring systems enable the thrusters to rotate between a hoverposition, wherein the thrust vectors are in a generally verticalorientation providing lift to the aircraft, and a forward-flightposition, wherein the thrust vectors are in a generally horizontalposition providing forward thrust to the aircraft.

At least one embodiment includes a main actuator configured to commonlyrotate the first and second spindle and a trim actuator configured torotate one of the first and second spindles relative to the other. Whenthe thrusters are in the hover position, the differential thrustvectoring system may rotate the thrusters relative to each other forproviding yaw and/or anti-torque functionality. When the thrusters arein the forward-flight position, the differential thrust vectoring systemmay rotate the thrusters relative to each other for providing rollfunctionality.

At least a second embodiment includes a single actuator and a planetarygear system coupled between the first and second spindles. The actuatorcauses both spindles to rotate, but the planetary gear system isconfigured to cause the first and second spindles to rotate at differentrates. In this embodiment, the thrust vectors are fixed in a generallyparallel orientation in the forward-flight position and the thrustvectors are automatically skewed to a predetermined deviation angle whenrotated to the hover position.

FIGS. 1 and 2 show an aircraft 100 that is convertible between aforward-flight mode, which allows for high-speed forward-flight as wellas horizontal takeoff and landing (shown in FIG. 1) and a hover mode,which allows for vertical takeoff and landing, hovering, and low speeddirectional movement (shown in FIG. 2). Aircraft 100 includes a fuselage102 coupled to an airframe housed therein, a tail section 104 includingvertical stabilizers 106 and horizontal stabilizers 108, a main rotor110 including a plurality of main rotor blades 112 configured to rotateabout a main mast axis 114, wings 116 extending from either side offuselage 102, a first thruster 118 positioned at an outboard end of onewing 116, and a second thruster 120 positioned at an outboard end of theother wing 116.

As best shown in FIG. 3, first thruster 118 comprises a ducted fanincluding a rotor assembly 122, a stator assembly 124, and a duct 126surrounding rotor assembly 122 and stator assembly 124. Rotor assembly122 includes a plurality of rotor blades 128 configured to rotate abouta mast axis 130. Rotation of rotor blades 128 about mast axis 130generates thrust along a first thrust vector 132 that is coaxial withmast axis 130. The direction of first thrust vector 132 may be modifiedby using a differential thrust vectoring system, as described below, torotate first thruster 118 about a tilt axis 134. Stator assembly 124 ispositioned downstream of rotor blades 128 and includes a stator hub 136centrally located within duct 126 and a plurality of stator vanes 138coupled between duct 126 and stator hub 136. Stator hub 136 houses amechanism therein configured to provide rotational energy to rotorassembly 122. The mechanism may comprise an electric motor configured toproduce rotational energy. Alternatively, the mechanism may comprise agearbox therein configured to deliver rotational energy to rotorassembly 122, wherein the gearbox receives rotational energy from adriveshaft passing through an attachment post 140 and the adjacentstator vane 138. The magnitude of first thrust vector 132 may bemodified by including collective control of the pitch of rotor blades128 and/or speed control of the mechanism configured to providerotational energy. To provide additional thrust control, stator vanes138 may be moveable. Movement of stator vanes 138 may enable firstthrust vector 132 to deviate from mast axis 130.

First thruster 118 and second thruster 120 are structurally similar. Assuch, second thruster 120 also comprises a ducted fan including a rotorassembly 142, a stator assembly 144, and a duct 146 surrounding rotorassembly 142 and stator assembly 144. Rotor assembly 142 includes aplurality of rotor blades 148 configured to rotate about a mast axis150. Rotation of rotor blades 148 about mast axis 150 generates thrustalong a second thrust vector 152 that is coaxial with mast axis 150. Thedirection of second thrust vector 152 may be modified by using adifferential thrust vectoring system, as described below, to rotatesecond thruster 120 about tilt axis 134. Stator assembly 144 ispositioned downstream of rotor blades 148 and includes a stator hub 156centrally located within duct 146 and a plurality of stator vanes 158coupled between duct 146 and stator hub 156. Stator hub 156 houses amechanism therein configured to provide rotational energy to rotorassembly 142. The mechanism may comprise an electric motor configured toproduce rotational energy. Alternatively, the mechanism may comprise agearbox therein configured to deliver rotational energy to rotorassembly 142, wherein the gearbox receives rotational energy from adriveshaft passing through an attachment post and the adjacent statorvane 158. The magnitude of second thrust vector 152 may be modified byincluding collective control of the pitch of rotor blades 148 and/orspeed control of the mechanism configured to provide rotational energy.To provide additional thrust control, stator vanes 158 may be moveable.Movement of stator vanes 158 may enable second thrust vector 152 todeviate from mast axis 150. While first thruster 118 and second thruster120 are shown as ducted fans, it should be understood that firstthruster 118 and second thruster 120 could comprise any type ofmechanism capable of producing thrust.

Referring again to FIG. 1, aircraft 100 is shown in forward-flight mode,wherein first thrust vector 132 and second thrust vector 152 aregenerally horizontal and in a substantially parallel relationship. Itshould be understood that first thrust vector 132 and second thrustvector 152 may deviate from parallel by a few degrees depending onairflow around fuselage 102. As such, for this specification and theclaims appended hereto, the phrase “substantially parallel” shouldinclude vectors within three degrees of parallelism. With first thruster118 and second thruster 120 generating forward thrust, lift is generatedby wings 116. Depending on the forward airspeed and the configuration ofwings 116, wings 116 may provide a substantial percentage of the liftrequired to maintain altitude. In this scenario, main rotor 110 maysimply be allowed to autorotate and maneuverability of aircraft 100 maybe provided by including rudders and/or elevators on the trailing endsof vertical stabilizers 106 and/or horizontal stabilizers 108,respectively. As discussed below, the differential thrust vectoringsystem may enable relative rotation of first thrust vector 132 andsecond thrust vector 152 providing roll functionality in forward-flightmode. If wings 116 do not provide sufficient lift, rotational energy isprovided to main rotor 110 and lift as well as directional thrust isgenerated by main rotor blades 112, which may be collectively orcyclically pitched. When rotational energy is provided to main rotor 110in forward-flight mode, vertical stabilizers 106 may provide sufficientanti-torque to counter the torque effects of main rotor 110.

Referring now to FIG. 2, aircraft 100 is shown in hover mode, whereinfirst thrust vector 132 and second thrust vector 152 are generallyvertical and are skewed. In hover mode, rotational energy is provided tomain rotor 110 and lift as well as directional thrust is generated bymain rotor blades 112, while first thruster 118 and second thruster 120generate additional lift. In addition, the skewed orientation of firstthrust vector 132 and second thrust vector 152 provides anti-torque toovercome the torque effects of main rotor 110. As described below, thedifferential thrust vectoring system may enable the angle between firstthrust vector 132 and second thrust vector 152 to vary, therebyproviding yaw control of aircraft 100. Yaw control may also be providedby adjusting the magnitude of first thrust vector 132 and/or secondthrust vector 152, as described above. Alternatively, or additionally,aircraft 100 may include other conventional anti-torque/yaw controlmechanisms such as a tail rotor or NOTAR system.

Referring now to FIGS. 4A-4C, a differential thrust vectoring system 200is illustrated with reference to use with aircraft 100. Differentialthrust vectoring system 200 includes a first thruster rotation assembly202, a second thruster rotation assembly 204, an actuator 206, and aplanetary gear system 208. As shown in FIGS. 4A and 4B, first thrusterrotation assembly 202 includes a first spindle 210 configured to becoupled to first thruster 118 for common rotation therewith about tiltaxis 134. First spindle 210 may include a flange for axial bolting toattachment post 140. Alternatively, or additionally, first spindle 210may fit inside attachment post 140, or attachment post 140 may fitinside first spindle 210, to provide for radial bolting. First spindle210 is rotatably coupled to a first pillow block assembly 212 whichincludes a first pedestal 214 and a second pedestal 216 axially spacedfrom first pedestal 214. First pedestal 214 and second pedestal 216 areconfigured to be coupled to the airframe via plates 218 and 220,respectively. First spindle 210 is rotatably coupled to first pedestal214 and second pedestal 216 via roller bearings 222 and 224,respectively. While first pillow block assembly 212 is shown with twopedestals, it should be understood that it may include one or more.

As shown in FIGS. 4B and 4C, second thruster rotation assembly 204includes a second spindle 226 configured to be coupled to secondthruster 120 for common rotation therewith about tilt axis 134. Secondspindle 226 may include a flange for axial bolting to the attachmentpost of second thruster 120. Alternatively, or additionally, secondspindle 226 may fit inside the attachment post, or the attachment postmay fit inside second spindle 226, to provide for radial bolting. Secondspindle 226 is rotatably coupled to a second pillow block assembly 228which includes a first pedestal 230 and a second pedestal 232 axiallyspaced from first pedestal 230. First pedestal 230 and second pedestal232 are configured to be coupled to the airframe via plates 234 and 236,respectively. Second spindle 226 is rotatably coupled to first pedestal230 and second pedestal 232 via roller bearings 238 and 240,respectively. While second pillow block assembly 228 is shown with twopedestals, it should be understood that it may include one or more.

As shown in FIG. 4A, planetary gear system 208 includes a ring gear 242,a plurality of planetary gears 244, and a sun gear 246. Ring gear 242 iscoupled to first spindle 210 for common rotation therewith about tiltaxis 134. Ring gear 242 includes a pair of tabs 248 configured torotatably couple ring gear 242 to actuator 206. As such, actuator 206 iscoupled to first spindle 210 through ring gear 242. However, actuator206 may be directly coupled to first spindle 210. Sun gear 246 is at thecenter of planetary gear system 208 and is fixed in position by abracket 250. Planetary gears 244 are coupled together via a planetarygear carrier 252 which includes a post 254 extending therefrom. As shownin FIG. 4C, planetary gear system 208 further includes a band 256coupled to second spindle 226. Band 256 includes a projection 258containing a roller bearing 260 configured to receive post 254 therein.While planetary gear system 208 is shown with a non-rotatable sun gear246, it should be understood that that instead, ring gear 242 may befixed and planetary gear carrier 252 is coupled to first spindle 210 andactuator 206 while sun gear is coupled for common rotation with secondspindle 226.

In operation, actuation of actuator 206 causes ring gear 242, firstspindle 210, and first thruster 118 to rotate together about tilt axis134. Because sun gear 246 is fixed, rotation of ring gear 242 causesplanetary gears 244, along with planetary gear carrier 252, band 256,second spindle 226, and second thruster 120, to also rotate about tiltaxis 134, but at a slower rate of rotation. That is, actuation ofactuator 206 will cause both first thruster 118 and second thruster 120to rotate about tilt axis 134, but first thruster 118 will rotatefurther than second thruster 120. This may be particularly useful on acompound helicopter. For example, in forward-flight mode of aircraft100, actuator 206 is in a first position wherein first thrust vector 132and second thrust vector 152 are substantially parallel (as shown inFIG. 1), and anti-torque is provided by vertical stabilizers 106. Whenit is desirable to transition to hover mode, actuator 206 is actuated toa second position, wherein first thrust vector 132 and second thrustvector 152 are skewed to a predetermined angle (as shown in FIG. 2).Because first thrust vector 132 has rotated past main mast axis 114 andsecond thrust vector 152 has not, the thrust produced along thosevectors provides anti-torque to overcome the torque effects generated bymain rotor 110.

While differential thrust vectoring system 200 is shown with actuator206 as a linear actuator, it should be understood that actuator 206 maycomprise a rotary actuator. Moreover, actuator 206 may be pneumatic,hydraulic, electric, or electromagnetic. In addition, differentialthrust vectoring system 200 may be configured such that failure ofactuator 206 results in first thruster 118 and second thruster 120automatically defaulting to either the hover position or the forwardflight position, depending on the mission of the aircraft 100 and thepreference for a vertical landing versus a horizontal landing.Furthermore, differential thrust vectoring system 200 may be configuredto permit a variety of types of power transfer therethrough to themechanisms configured to deliver rotational energy to rotor assembly 122and rotor assembly 142. For example, differential thrust vectoringsystem 200 may be configured to position a gearbox between firstthruster rotation assembly 202 and second thruster rotation assembly 204wherein a first driveshaft may pass through an opening in sun gear 246and extend through first spindle 210 to provide rotational energy tofirst rotor assembly 122 and a second driveshaft may pass through secondspindle 226 to provide rotational energy to second rotor assembly 142.Alternatively, first spindle 210 and second spindle 226 may beconfigured to pass electrical power via cables to electric motors housedwithin stator hub 136 and stator hub 156 or pass hydraulic power viatubing to hydraulic motors housed with stator hub 136 and stator hub156. First spindle 210 and second spindle 226 may be configured to passthe cables or tubing through the entire lengths thereof and/or they mayinclude openings in the sidewalls configured to pass the cables ortubing therethrough.

Referring now to FIGS. 5A and 5B, a differential thrust vectoring system300 is illustrated with reference to use with aircraft 100. Differentialthrust vectoring system 300 includes a first thruster rotation assembly302, a second thruster rotation assembly 304, a linear main actuator306, and a linear trim actuator assembly 308. First thruster rotationassembly 302 includes a first spindle 310 configured to be coupled tofirst thruster 118 for common rotation therewith about tilt axis 134.First spindle 310 may include a flange for axial bolting to attachmentpost 140. Alternatively, or additionally, first spindle 310 may fitinside attachment post 140, or attachment post 140 may fit inside firstspindle 310, to provide for radial bolting. First spindle 310 isrotatably coupled to a first pillow block assembly 312 which includes afirst pedestal 314 and a second pedestal 316 axially spaced from firstpedestal 314. First pedestal 314 and second pedestal 316 are configuredto be coupled to the airframe via plates 318 and 320, respectively.First spindle 310 is rotatably coupled to first pedestal 314 and secondpedestal 316 via roller bearings 322 and 324, respectively. While firstpillow block assembly 312 is shown with two pedestals, it should beunderstood that it may include one or more.

Second thruster rotation assembly 304 includes a second spindle 326configured to be coupled to second thruster 120 for common rotationtherewith about tilt axis 134. Second spindle 326 may include a flangefor axial bolting to the attachment post of second thruster 120.Alternatively, or additionally, second spindle 326 may fit inside theattachment post, or the attachment post may fit inside second spindle326, to provide for radial bolting. Second spindle 326 is rotatablycoupled to a second pillow block assembly 328 which includes a firstpedestal 330 and a second pedestal 332 axially spaced from firstpedestal 330. First pedestal 330 and second pedestal 332 are configuredto be coupled to the airframe via plates 334 and 336, respectively.Second spindle 326 is rotatably coupled to first pedestal 330 and secondpedestal 332 via roller bearings 338 and 340, respectively. While secondpillow block assembly 328 is shown with two pedestals, it should beunderstood that it may include one or more.

Linear trim actuator assembly 308 includes a ring 342 coupled to firstspindle 310, a band 356 coupled to second spindle 326, and a linear trimactuator 344 coupled between ring 342 and band 356. Ring 342 includes apair of tabs 348 configured to rotatably couple ring 342 to linear mainactuator 306. As such, linear main actuator 306 is coupled to firstspindle 310 through ring 342. However, linear main actuator 306 may bedirectly coupled to first spindle 310. Ring 342 further includes aprojection 346 configured to rotatably couple to linear trim actuator344. Band 356 includes also includes a projection 350 configured torotatably couple to linear trim actuator 344.

In operation, actuation of linear main actuator 306 causes ring 342,first spindle 310, and first thruster 118 to rotate together about tiltaxis 134. Because ring 342 is coupled to band 356 via linear trimactuator 344, second spindle 326 and second thruster 120 also rotateabout tilt axis 134 in response to actuation of linear main actuator306. Differential rotation of first thruster 118 and second thruster 120is provided by linear trim actuator 344. That is, actuation of lineartrim actuator 344 causes band 356, second spindle 326, and secondthruster 120 to rotate relative to ring 342, first spindle 310, andfirst thruster 118. Accordingly, in forward-flight mode of aircraft 100,both linear main actuator 306 and linear trim actuator 344 are in firstpositions, wherein first thrust vector 132 and second thrust vector 152are substantially parallel (as shown in FIG. 1), and anti-torque isprovided by vertical stabilizers 106. When it is desirable to transitionto hover mode, both linear main actuator 306 and linear trim actuator344 are actuated to second positions, and first thrust vector 132 andsecond thrust vector 152 are skewed to a predetermined angle (as shownin FIG. 2). Because first thrust vector 132 has rotated past main mastaxis 114 and second thrust vector 152 has not, the thrust produced alongthose vectors provides anti-torque to overcome the torque effectsgenerated by main rotor 110. Further actuation of linear main actuator306 and linear trim actuator 344 can further vary the angle betweenfirst thrust vector 132 and second thrust vector 152, thereby varyingthe rotational force on aircraft 100 and providing yaw control. The sameprincipal can be applied during forward-flight mode. That is, deviationof first thrust vector 132 and second thrust vector 152 from thesubstantially parallel orientation during forward flight can provideroll capabilities.

Linear main actuator 306 and linear trim actuator 344 may be pneumatic,hydraulic, electric, or electromagnetic. In addition, differentialthrust vectoring system 300 may be configured such that failure oflinear main actuator 306 and/or linear trim actuator 344 results infirst thruster 118 and second thruster 120 automatically defaulting toeither the hover position or the forward-flight position, depending onthe mission of the aircraft 100 and the preference for a verticallanding versus a horizontal landing. Furthermore, differential thrustvectoring system 300 may be configured to permit a variety of types ofpower transfer therethrough to the mechanisms configured to deliverrotational energy to rotor assembly 122 and rotor assembly 142. Forexample, differential thrust vectoring system 300 may be configured toposition a gearbox between first thruster rotation assembly 302 andsecond thruster rotation assembly 304 wherein a first driveshaft maypass through first spindle 310 to provide rotational energy to firstrotor assembly 122 and a second driveshaft may pass through secondspindle 326 to provide rotational energy to second rotor assembly 142.Alternatively, first spindle 310 and second spindle 326 may beconfigured to pass electrical power via cables to electric motors housedwithin stator hub 136 and stator hub 156 or pass hydraulic power viatubing to hydraulic motors housed with stator hub 136 and stator hub156. First spindle 310 and second spindle 326 may be configured to passthe cables or tubing through the entire lengths thereof and/or they mayinclude openings in the sidewalls configured to pass the cables ortubing therethrough.

Referring now to FIGS. 6A-6C, a differential thrust vectoring system 400is illustrated with reference to use with aircraft 100. Differentialthrust vectoring system 400 includes a first thruster rotation assembly402, a second thruster rotation assembly 404, a rotary main actuator406, and a rotary trim actuator assembly 408. As shown in FIGS. 6A and6B, first thruster rotation assembly 402 includes a first spindle 410configured to be coupled to first thruster 118 for common rotationtherewith about tilt axis 134. First spindle 410 may include a flangefor axial bolting to attachment post 140. Alternatively, oradditionally, first spindle 410 may fit inside attachment post 140, orattachment post 140 may fit inside first spindle 410, to provide forradial bolting. First spindle 410 is rotatably coupled to a first pillowblock assembly 412 which includes a first pedestal 414 and a secondpedestal 416 axially spaced from first pedestal 414. First pedestal 414and second pedestal 416 are configured to be coupled to the airframe viaplates 418 and 420, respectively. First spindle 410 is rotatably coupledto first pedestal 414 and second pedestal 416 via roller bearings 422and 424, respectively. While first pillow block assembly 412 is shownwith two pedestals, it should be understood that it may include one ormore.

As shown in FIGS. 6B and 6C, second thruster rotation assembly 404includes a second spindle 426 configured to be coupled to secondthruster 120 for common rotation therewith about tilt axis 134. Secondspindle 426 may include a flange for axial bolting to the attachmentpost of second thruster 120. Alternatively, or additionally, secondspindle 426 may fit inside the attachment post, or the attachment postmay fit inside second spindle 426, to provide for radial bolting. Secondspindle 426 is rotatably coupled to a second pillow block assembly 428which includes a first pedestal 430 and a second pedestal 432 axiallyspaced from first pedestal 430. First pedestal 430 and second pedestal432 are configured to be coupled to the airframe via plates 434 and 436,respectively. Second spindle 426 is rotatably coupled to first pedestal430 and second pedestal 432 via roller bearings 438 and 440,respectively. While second pillow block assembly 428 is shown with twopedestals, it should be understood that it may include one or more.

Rotary trim actuator assembly 408 includes a first ring gear 442 coupledto first spindle 410, a second ring gear 456 coupled to second spindle426, and a rotary trim actuator 444 coupled between first ring gear 442and second ring gear 456. First ring gear 442 includes external teeth448 configured to mesh with external teeth 446 of rotary main actuator406. As such, rotary main actuator 406 is coupled to first spindle 410through first ring gear 442. First ring gear 442 further includes abracket 450 configured to couple rotary trim actuator 444 thereto.Second ring gear 456 includes internal teeth 452 configured to mesh withexternal teeth 454 of rotary trim actuator 444.

In operation, actuation of rotary main actuator 406 causes first ringgear 442, first spindle 410, and first thruster 118 to rotate togetherabout tilt axis 134. Because first ring gear 442 is coupled to secondring gear 456 via rotary trim actuator 444, second spindle 426 andsecond thruster 120 also rotate about tilt axis 134 in response toactuation of rotary main actuator 406. Differential rotation of firstthruster 118 and second thruster 120 is provided by rotary trim actuator444. That is, actuation of rotary trim actuator 444 causes second ringgear 456, second spindle 426, and second thruster 120 to rotate relativeto first ring gear 442, first spindle 410, and first thruster 118.Accordingly, in forward-flight mode of aircraft 100, both rotary mainactuator 406 and rotary trim actuator 444 are in first positions,wherein first thrust vector 132 and second thrust vector 152 aresubstantially parallel (as shown in FIG. 1), and anti-torque is providedby vertical stabilizers 106. When it is desirable to transition to hovermode, both rotary main actuator 406 and rotary trim actuator 444 areactuated to second positions, and first thrust vector 132 and secondthrust vector 152 are skewed to a predetermined angle (as shown in FIG.2). Because first thrust vector 132 has rotated past main mast axis 114and second thrust vector 152 has not, the thrust produced along thosevectors provides anti-torque to overcome the torque effects generated bymain rotor 110. Further actuation of rotary main actuator 406 and rotarytrim actuator 444 can further vary the angle between first thrust vector132 and second thrust vector 152, thereby varying the rotational forceon aircraft 100 and providing yaw control. The same principal can beapplied during forward-flight mode. That is, deviation of first thrustvector 132 and second thrust vector 152 from the substantially parallelorientation during forward flight can provide roll capabilities.

Rotary main actuator 406 and rotary trim actuator 444 may be pneumatic,hydraulic, electric, or electromagnetic. In addition, differentialthrust vectoring system 400 may be configured such that failure ofrotary main actuator 406 and/or rotary trim actuator 444 results infirst thruster 118 and second thruster 120 automatically defaulting toeither the hover position or the forward-flight position, depending onthe mission of the aircraft 100 and the preference for a verticallanding versus a horizontal landing. Furthermore, differential thrustvectoring system 400 may be configured to permit a variety of types ofpower transfer therethrough to the mechanisms configured to deliverrotational energy to rotor assembly 122 and rotor assembly 142. Forexample, differential thrust vectoring system 400 may be configured toposition a gearbox between first thruster rotation assembly 402 andsecond thruster rotation assembly 404 wherein a first driveshaft maypass through first spindle 410 to provide rotational energy to firstrotor assembly 122 and a second driveshaft may pass through secondspindle 426 to provide rotational energy to second rotor assembly 142.Alternatively, first spindle 410 and second spindle 426 may beconfigured to pass electrical power via cables to electric motors housedwithin stator hub 136 and stator hub 156 or pass hydraulic power viatubing to hydraulic motors housed with stator hub 136 and stator hub156. First spindle 410 and second spindle 426 may be configured to passthe cables or tubing through the entire lengths thereof and/or they mayinclude openings in the sidewalls configured to pass the cables ortubing therethrough.

While differential thrust vectoring systems 200, 300, and 400 arereferenced for use with aircraft 100, a compound helicopter, it shouldbe understood that they may be utilized on any aircraft that may benefitfrom altering the thrust vectors of a pair of thrusters.

At least one embodiment is disclosed, and variations, combinations,and/or modifications of the embodiment(s) and/or features of theembodiment(s) made by a person having ordinary skill in the art arewithin the scope of the disclosure. Alternative embodiments that resultfrom combining, integrating, and/or omitting features of theembodiment(s) are also within the scope of the disclosure. Wherenumerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example,whenever a numerical range with a lower limit, R_(l), and an upperlimit, R_(u), is disclosed, any number falling within the range isspecifically disclosed. In particular, the following numbers within therange are specifically disclosed: R=R₁+k*(R_(u)−R_(l)), wherein k is avariable ranging from 1 percent to 100 percent with a 1 percentincrement, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5percent, . . . 50 percent, 51 percent, 52 percent, . . . , 95 percent,96 percent, 95 percent, 98 percent, 99 percent, or 100 percent.Moreover, any numerical range defined by two R numbers as defined in theabove is also specifically disclosed. Use of the term “optionally” withrespect to any element of a claim means that the element is required, oralternatively, the element is not required, both alternatives beingwithin the scope of the claim. Use of broader terms such as comprises,includes, and having should be understood to provide support fornarrower terms such as consisting of, consisting essentially of, andcomprised substantially of. Accordingly, the scope of protection is notlimited by the description set out above but is defined by the claimsthat follow, that scope including all equivalents of the subject matterof the claims. Each and every claim is incorporated as furtherdisclosure into the specification and the claims are embodiment(s) ofthe present invention. Also, the phrases “at least one of A, B, and C”and “A and/or B and/or C” should each be interpreted to include only A,only B, only C, or any combination of A, B, and C.

What is claimed is:
 1. A differential thrust vectoring system,comprising: a first spindle configured to be coupled for common rotationabout a tilt axis with a first thruster; a second spindle configured tobe coupled for common rotation about the tilt axis with a secondthruster; a main actuator configured to be coupled between the firstspindle and an airframe; and a trim actuator coupled between the firstspindle and the second spindle; wherein the differential thrustvectoring system is configured such that actuation of the main actuatorwould cause common rotation about the tilt axis of the first spindle andthe second spindle and actuation of the trim actuator would causerotation about the tilt axis of the second spindle relative to the firstspindle.
 2. The differential thrust vectoring system of claim 1, whereinthe main actuator is either a linear actuator or a rotary actuator andthe trim actuator is either a linear actuator or a rotary actuator, andthe main actuator is one of pneumatic, hydraulic, electric, andelectromagnetic, and the trim actuator is one of pneumatic, hydraulic,electric, and electromagnetic.
 3. The differential thrust vectoringsystem of claim 1, wherein the first spindle and the second spindle areconfigured to transmit at least one of mechanical, electrical, andhydraulic power therethrough.
 4. The differential thrust vectoringsystem of claim 1, wherein the differential thrust vectoring system isconfigured such that failure of the trim actuator and/or the mainactuator will result in thrust vectors of the first thruster and thesecond thruster assuming a substantially parallel relationship.
 5. Thedifferential thrust vectoring system of claim 1, wherein thedifferential thrust vectoring system is configured such that failure ofthe trim actuator and/or the main actuator will result in thrust vectorsof the first thruster and the second thruster assuming a predeterminedskewed relationship.
 6. The differential thrust vectoring system ofclaim 1, wherein the trim actuator is configured to move between a firstposition, wherein a first thrust vector of the first thruster issubstantially parallel to a second thrust vector of the second thruster,and a second position, wherein the first thrust vector is askew to thesecond thrust vector.
 7. A differential thrust vectoring system,comprising: a first spindle configured to be coupled for common rotationabout a tilt axis with a first thruster; a second spindle configured tobe coupled for common rotation about the tilt axis with a secondthruster; a rotary main actuator configured to be coupled between thefirst spindle and an airframe; and a rotary trim actuator coupledbetween the first spindle and the second spindle; wherein thedifferential thrust vectoring system is configured such that actuationof the main actuator would cause common rotation about the tilt axis ofthe first spindle and the second spindle and actuation of the trimactuator would cause rotation about the tilt axis of the second spindlerelative to the first spindle.
 8. The differential thrust vectoringsystem of claim 7, wherein the main actuator is one of pneumatic,hydraulic, electric, and electromagnetic, and the trim actuator is oneof pneumatic, hydraulic, electric, and electromagnetic.
 9. Thedifferential thrust vectoring system of claim 7, wherein the firstspindle and the second spindle are configured to transmit at least oneof mechanical, electrical, and hydraulic power therethrough.
 10. Thedifferential thrust vectoring system of claim 7, wherein thedifferential thrust vectoring system is configured such that failure ofthe trim actuator and/or the main actuator will result in thrust vectorsof the first thruster and the second thruster assuming a substantiallyparallel relationship.
 11. The differential thrust vectoring system ofclaim 7, wherein the differential thrust vectoring system is configuredsuch that failure of the trim actuator and/or the main actuator willresult in thrust vectors of the first thruster and the second thrusterassuming a predetermined skewed relationship.
 12. The differentialthrust vectoring system of claim 7, wherein the trim actuator isconfigured to move between a first position, wherein a first thrustvector of the first thruster is substantially parallel to a secondthrust vector of the second thruster, and a second position, wherein thefirst thrust vector is askew to the second thrust vector.
 13. Thedifferential thrust vectoring system of claim 7, wherein the firstspindle comprises a ring gear, and the main actuator comprises a gearengaged with the ring gear of the first spindle.
 14. The differentialthrust vectoring system of claim 7, wherein the second spindle comprisesa ring gear, and the trim actuator comprises a gear engaged with thering gear of the second spindle.
 15. An aircraft, comprising: afuselage; an airframe; a first thruster having a first thrust vector; asecond thruster having a second thrust vector; and a differential thrustvectoring system, comprising: a first spindle coupled for commonrotation about a tilt axis with the first thruster; a second spindlecoupled for common rotation about the tilt axis with the secondthruster; and a main actuator coupled between the first spindle and theairframe; a trim actuator coupled between the first spindle and thesecond spindle; wherein the differential thrust vectoring system isconfigured such that actuation of the main actuator causes rotationabout the tilt axis of the first spindle and the second spindle; andwherein the differential thrust vectoring system is configured such thatactuation of the trim actuator causes rotation about the tilt axis ofthe second spindle relative to the first spindle.
 16. The aircraft ofclaim 15, further comprising: a main rotor; wherein when the actuator isin a forward-flight position the first thrust vector and the secondthrust vector are substantially parallel and when the actuator is in ahover position the first thrust vector and the second thrust vector areskewed, wherein an angle between the first thrust vector and the secondthrust vector are configured to counter a torque effect of the mainrotor.
 17. The aircraft of claim 16, further comprising: a verticalstabilizer configured to counter the torque effect of the main rotorduring forward flight.
 18. The aircraft of claim 15, wherein the firstthruster and the second thruster comprise ducted fans.
 19. The aircraftof claim 16, wherein the actuators are configured to assume the hoverposition in failure.
 20. The aircraft of claim 15, wherein thedifferential thrust vectoring system is configured such that failure ofthe trim actuator and/or the main actuator will result in the firstthrust vector and the second thrust vector assuming a substantiallyparallel relationship or a predetermined skewed relationship.